Standard Model of Particle Physics - Max Planck Society · Schöning/Rodejohann 2 Standard Model of Particle Physics SS 2013 Contents PART I Determination of the CKM Matrix

Schöning/Rodejohann 1 Standard Model of Particle Physics SS 2013

Lecture:

Standard Model of Particle Physics

Heidelberg SS 2013

Flavour Physics I + II


ContentsPART I

Determination of the CKM Matrix

CP Violation in Kaon system

CP violation in the B-system

PART II

Search for Flavor Violating Neutral Currents (Lepton Flavor Violation)

Search for Lepton/Baryon Number Violation


Flavour Changing Neutral Currents...are forbidden in the SM at tree level (GIM mechanism)

d

b

γ, Z

μ-

γ, Z

μ+

branching ratio=0

d

b

γ, Z

μ-

γ, Z

μ+

t

W

W

penguin diagram

branching ratio enhanced by new physics!

arXiv:1112.3564


Recent Results from LHCBSearch for

Bs → μ+μ

−

(95% CL) SM expected 1.1 x 10-10

SM expected 3.2 x 10-9

well compatible with SM expectation

not much room for physics beyond the SM

ATLAS and CMS also looking into this channel


Lepton Flavor Violation (FCNC)...also forbidden in the SM at tree level (GIM mechanism)

γ, Z

μ-

γ, Z

μ+

branching ratio=0

γ, Z

μ-

γ, Z

μ+W

W

penguin diagram

branching ratio largely enhanced by new physics (40 orders of magnitude)!

μ-

τ+

μ-

τ+

ν(Δmν

2)2

mW4 ≈ 10−50

suppressed


● Neutrino Oscillations: solar neutrinos reactor neutrinos atmospheric neutrinos neutrino beams

P =sin22sin21.27m2 LE

μ

W W

l

ν1ν

2

Discovery of Neutrino OscillationsDiscovery of Neutrino Oscillations


Cabibbo Kobayashi Maskawa (CKM) Pontecorvo Maki Nakagawa Sakata (PMNS)

Quarks Leptons

d 's 'b ' =

V ud V us V ub

V cd V cs V cb

V td V ts V tbdsb

e

=

V e1 V e2 V e3

V 1 V 2 V 3

V 1 V 2 V 3

1

2

3

Fermion MixingFermion Mixing

● W bosons smell different flavors!● other gauge bosons (γ, Z, g) do not (→ no FCNC)


Cabibbo Kobayashi Maskawa (CKM) Pontecorvo Maki Nakagawa Sakata (PMNS)

Quarks Leptons

d 's 'b ' =

0.974 0.225 0.0030.225 0.973 0.0410.009 0.040 0.999

dsb

e

≈0.816 0.577 0.2

0.408 0.577 0.7070.408 0.577 0.707

1

2

3

● W bosons smell different flavors!● other gauge bosons (γ, Z, g) do not (→ no FCNC)

Fermion MixingFermion Mixing


quark flavor not conserved(family number changes)

lepton flavor not conservedbut difficult to observe!

(concept of families right?)

Family Number ViolationFamily Number Violation Flavor Changing neutral currents are forbidden!

Lepton Flavor Number in Charged Currents is an “adhoc” concept

light andsmall mass splitting


Lepton Decays:

μ→ e γ μ→ eee

τ→ e(μ) γ τ→ l l l (l=e,μ) τ→ l h

Conversion (μ-Capture):

μ N → e N

Fixed Target Experiments:

μ N → τ N e N → μ(τ) N

Collider Experiments:

e p → μ(τ) X

Z' → l l'χ0,± → l l' X

Meson Decays: Φ, K → ll' D, J/ψ → ll' B, Υ → ll'

LFV

proposedproposed

LHC

HERA

Overview LFV ExperimentsOverview LFV Experiments


But (Charged) Lepton Flavor Violation not seen:

The SM prediction for Lepton Flavor Violating (LFV) Processes is negligible (GIM-like suppression)

Any sign of LFV would manifestNew Physics

Charged Lepton Flavour Violation Leptons mix in a similar way as quarks (→ PMNS matrix, W.R next week)

Lepton mixing discovered in neutrino oscillations

muon to electron conversion experiments


Muon-Electron Conversion

μ

μ N → e N conversion

muon capture in nucleons muon decays in orbit


SINDRUM II Result

no sign of a signal!

μ N → e N conversion

electron receives kineticenergy from muon mass minus nuclear recoil energy

μ- N

e- N


But (Charged) Lepton Flavor Violation not seen:

The SM prediction for Lepton Flavor Violating (LFV) Processes is negligible (GIM-like suppression)

Any sign of LFV would manifestNew Physics

Charged Lepton Flavour Violation Leptons mix in a similar way as quarks (→ PMNS matrix, W.R next week)

Lepton mixing discovered in neutrino oscillations

muon to electron conversion experiments


Limitation: accidental background

better space resolutionimprove tracking

current limit: BR(μ+ → e+ γ) < 5.7 x 10 – 13

MEGstart 2007 (MEGA: 10 - 1 1)

The MEG ExperimentThe MEG Experiment

still taking data upgrade planned starting next year

LFV decay: μ+ → e+ γ


Mu3e ExperimentSearch for the decay: μ→ eee SM prediction: B(μ→ eee)≪10−50

current limit B(μ→ eee)< 10−12

Design and construction: Heidelberg

planned sensitivity: B(μ→ eee)< 10−16

will be performed at the Paul Scherrer Institute (PSI) in 2014+

e-

X

μ+

e-

e+


Baryon and Lepton Number ViolationProton is stable: τ > 1031−1033 years

p→π0 e+

No observation of Baryon or Lepton Number Violation!

π + → e+ γ

Not seen:

p→π+ γ

However, baryon or lepton number violating processes are required to explainmatter antimatter asymmetry in universe

The fact the humans and life exists on earth (no radiation damage) excludesalready BSM scenarios!

New BSM Physics is required!

Super Kamiokande


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Standard Model of Particle Physics - Max Planck Society · Schöning/Rodejohann 2 Standard Model of Particle Physics SS 2013 Contents PART I Determination of the CKM Matrix